1. Field of the Invention
The present invention relates to stable foamed cement slurries.
More particularly, the present invention relates to stable foamed cement slurries, where the slurries comprise a cement, a foaming system including an ionic foaming agent including a surfactant and an anionic polymer or a cationic polymer with or without a zwitterionic surfactant. The foamed cements of this invention have improved foam characteristics showing improvements from about 10% to about 80% at atmospheric pressure and produce foams stable at temperatures from room temperature to about 350° F.
2. Description of the Related Art
The use of foaming agents to provide lightweight cement compositions was first shown in U.S. Pat. No. 5,711,801 to Chatterji et. al., where the slurry density ranged from about 6 to about 16 pounds per gallon by adding 5% to 80% by volume of gas phase to form the resulting foamed composition. Subsequently, U.S. Pat. Nos. 5,897,699; 5,900,053; 5,966,693; 6,063,738; 6,227,294; 6,244,343; 6,336,505; 6,364,945; 6,367,550; 6,547,871; 6,797,054; 6,619,399; 6,955,294; 6,336,505; 6,953,505; 6,835,243; 7,008,477; 7,013,975; and 7,191,834 describe the use of foamer and foam stabilizer based surfactant systems like alpha-olefinic sulfonated, ethoxylated alcohol ether sulfate surfactant, alkyl or alkene amidopropyl betaine surfactant alkyl or alkene amidopropyl dimethyl amine oxide, hydrolyzed keratin, ammonium salt of an alkyl ether sulfate, cocamidopropyl hydroxysultaine, cocoamidopropyl dimethyloxide, capryl/capramido propyl betaine, capryl/capramido propyl dimethyl amine oxide. U.S. Pat. No. 6,235,809 disclosed the use of sodium polyacrylate and AMPS terpolymer to stabilize foamed cement systems.
Although a number of foamed cement compositions are well known, there is still a need in the art for additional foamed cement composition, especially compositions having improved foam characteristics.